Yingying Yang
Dalian University of Technology, China
Title: Theoretical study on transition-metal carbide system as cathode catalyst in Li-O2 batteries
Biography
Biography: Yingying Yang
Abstract
Lithium-oxygen (Li-O2) batteries have recently attracted extensive attention due to their high theoretical energy density and practically available energy density, which are essential for future electric vehicles and other high-energy storage devices. However, the sluggish charging and discharging kinetic rates limit its practical application, and suffers from many issues such as high ORR/OER overpotential, short cycle life, low current density, unstable electrode material, and electrolyte instability. One of the approaches to accelerate the sluggish electrochemical reactions is using electrocatalysts. In this paper, the first-principles calculation method is used to study the cathode catalysts in Li-O2 batteries based on transition-metal carbides (TMCs) system, including: to study the reaction mechanism during charging and discharging processes in lithium-air batteries; to build the theoretical model coupling of electron, ion, and interface in electrochemical reaction to determine the thermodynamics evaluation parameters of catalytic activity; to exploit the structure-activity relationship in electrochemical reactions, thereby determining the intrinsic properties affecting the catalytic activity. Finally, our work provides reliable information for the design, screening and development of new materials for Li-O2 batteries. The detailed studies are as follows: oxidized TiC surface as the potential state of TiC cathode is analyzed during OER, in which O layer helps O22- oxidation and Li-O bond activation, showing smaller O2 evolution barrier and lower charge voltage; doping effect on the catalytic activity of TiC; correlations between material properties relative to the adsorption/desorption behavior of active molecules and the catalytic activity of 3d-TMCs and early TMCs are constructed, in which the ORR overpotentials are inversely proportional to the Li4O2/LiO2 adsorption energies, meanwhile, the ORR overpotentials are proportional to the desorption energies of Li+ and the OER overpotentials are proportional to the O2 desorption energies. Besides, the study on catalytic activity of Ti2C MXene in Li-O2 is under way.